gpllib: Add parse_partition_table() to iterate through all partitions on a disk

Impact: expand gpllib disk API

parse_partition_table() can be used to execute a callback on each partition.

The signature of the callback is:

   void callback(struct driveinfo *drive_info,
                struct part_entry *ptab,
                struct part_entry *ptab_root,
                int offset_root,
                int local_partition_number,
                int ebr_seen)

 * drive_info represents the disk.
 * ptab is the current partition entry processed.
 * ptab_root is the partition entry linking to the current one processed (extended only).
 * offset_root is the offset of the ebr when iterating through extended partitions
   (0 otherwise).
 * local_partition_number is the number of the partition processed (0->3).
 * ebr_seen counts the total number of ebr processed.

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>

3 files changed, 158 insertions, 1 deletions

diff --git a/com32/gplinclude/disk/msdos.h b/com32/gplinclude/disk/msdos.h
new file mode 100644
index 00000000..b6dd9481
--- /dev/null
+++ b/com32/gplinclude/disk/msdos.h
@@ -0,0 +1,8 @@
+#ifndef _MSDOS_H_
+#define _MSDOS_H_
+
+#include <disk/geom.h>
+
+int parse_partition_table(struct driveinfo *, void *, int *);
+
+#endif /* _MSDOS_H_ */
diff --git a/com32/gpllib/Makefile b/com32/gpllib/Makefile
index 7897af58..83f1407a 100644
--- a/com32/gpllib/Makefile
+++ b/com32/gpllib/Makefile
@@ -10,7 +10,7 @@ REQFLAGS += -I../gplinclude
 
 LIBOBJS  = dmi/dmi_battery.o dmi/dmi_chassis.o dmi/dmi_memory.o            \
            dmi/dmi_processor.o dmi/dmi.o dmi/dmi_bios.o dmi/dmi_base_board.o \
-	   dmi/dmi_ipmi.o cpuid.o disk/geom.o disk/read.o disk/write.o \
+	   dmi/dmi_ipmi.o cpuid.o disk/geom.o disk/read.o disk/write.o disk/msdos.o \
 	   disk/util.o disk/labels.o disk/swsusp.o disk/error.o vpd/vpd.o
 
 BINDIR   = /usr/bin
diff --git a/com32/gpllib/disk/msdos.c b/com32/gpllib/disk/msdos.c
new file mode 100644
index 00000000..da28b8bb
--- /dev/null
+++ b/com32/gpllib/disk/msdos.c
@@ -0,0 +1,149 @@
+#include <stdlib.h>
+#include <disk/geom.h>
+#include <disk/partition.h>
+#include <disk/read.h>
+
+static inline int is_extended_partition(struct part_entry *ptab)
+{
+	return (ptab->ostype == 0x05 ||
+		ptab->ostype == 0x0f ||
+		ptab->ostype == 0x85);
+}
+static inline int msdos_magic_present(char *ptab)
+{
+	return ( *(uint16_t *)(ptab + 0x1fe) == 0xaa55 );
+}
+
+/**
+ * process_ebr - execute a callback for each partition contained in an ebr
+ * @drive_info:	driveinfo struct describing the drive
+ * @ptab_root:	part_entry struct describing the root partition (pointing to the ebr)
+ * @ebr_seen:	Number of ebr processed
+ * @callback:	Callback to execute
+ **/
+static void process_ebr(struct driveinfo *drive_info, struct part_entry *ptab_root,
+		        int ebr_seen,
+		        void *callback(struct driveinfo *, struct part_entry *, struct part_entry *, int, int, int),
+		        int *error, int offset_root)
+{
+	/* The ebr is located at the first sector of the extended partition */
+	char* ebr = read_sectors(drive_info, ptab_root->start_lba+offset_root, 1, error);
+	if (!ebr)
+		return;
+
+	/* Check msdos magic signature */
+	if(!msdos_magic_present(ebr))
+		return;
+	ebr_seen += 1;
+
+	struct part_entry *ptab_child = (struct part_entry *)(ebr + PARTITION_TABLES_OFFSET);
+
+	/* First process the data partitions */
+	for (int i = 0; i < 4; i++) {
+		if (*error)
+			return;
+
+		if (ptab_child[i].start_sect > 0) {
+			if (is_extended_partition(&ptab_child[i])) {
+				continue;
+			}
+
+			/* Check for garbage in the 3rd and 4th entries */
+			if (i > 2) {
+				unsigned int offset = ptab_child->start_lba + ptab_root->start_lba;
+				if ( offset + ptab_child->length <= ptab_root->start_lba ||
+				     offset >= ptab_root->start_lba + ptab_root->length ) {
+					continue;
+				}
+			}
+			callback(drive_info,
+				 &ptab_child[i],
+				 ptab_root,
+				 offset_root,
+				 i,
+				 ebr_seen);
+		}
+	}
+
+	/* Now process the extended partitions */
+	for (int i = 0; i < 4; i++) {
+		if (is_extended_partition(&ptab_child[i])) {
+			callback(drive_info,
+				 &ptab_child[i],
+				 ptab_root,
+				 offset_root,
+				 i,
+				 ebr_seen);
+			process_ebr(drive_info, &ptab_child[i], ebr_seen + 1, callback, error, ptab_root->start_lba);
+		}
+	}
+}
+
+/**
+ * process_mbr - execute a callback for each partition contained in an {m,e}br
+ * @drive_info:	driveinfo struct describing the drive
+ * @ptab:	Pointer to the partition table
+ * @callback:	Callback to execute
+ * @error:	Return the error code (I/O), if needed
+ **/
+static void process_mbr(struct driveinfo *drive_info, struct part_entry *ptab,
+		        void *callback(struct driveinfo *, struct part_entry *, struct part_entry *, int, int, int),
+		        int *error)
+{
+	for (int i = 0; i < 4; i++) {
+		if (*error)
+			return;
+
+		if (ptab[i].start_sect > 0) {
+			if (is_extended_partition(&ptab[i])) {
+				callback(drive_info,
+					 &ptab[i],
+					 ptab,
+					 0,
+					 i,
+					 0);
+				process_ebr(drive_info, &ptab[i], 0, callback, error, 0);
+			} else
+				callback(drive_info,
+					 &ptab[i],
+					 ptab,
+					 0,
+					 i,
+					 0);
+		}
+	}
+}
+
+/**
+ * parse_partition_table - execute a callback for each partition entry
+ * @d:		driveinfo struct describing the drive
+ * @callback:	Callback to execute
+ * @error:	Return the error code (I/O), if needed
+ *
+ * The signature of the callback should be the following:
+ *
+ * void callback(struct driveinfo *drive_info,
+ *		 struct part_entry *ptab,
+ *		 struct part_entry *ptab_root,
+ *		 int offset_root,
+ *		 int local_partition_number,
+ *		 int ebr_seen)
+ **/
+int parse_partition_table(struct driveinfo *d, void *callback, int *error)
+{
+	char *mbr = read_mbr(d->disk, error);
+	if (!mbr)
+		return -1;
+	else {
+		/* Check msdos magic signature */
+		if (!msdos_magic_present(mbr))
+			return -1;
+
+		struct part_entry *ptab = (struct part_entry *)(mbr + PARTITION_TABLES_OFFSET);
+		process_mbr(d, ptab, callback, error);
+		if (*error)
+			return -1;
+		else
+			return 0;
+	}
+}